Rhetoric: Alma does not separate temporal and spiritual worlds. The flight from Jerusalem, journeys in the wilderness, and the conflicts in the New World were temporal and physical. Then, Alma immediately adds that these mortal dangers might also have included spiritual danger.
This combination of factors allows Alma both to invoke the histories of real conflicts and also to emphasize their spiritual meanings. Fear of spiritual destruction is not simply a rhetorical device, however. Had the people of Nephi been conquered by their surrounding world, their understanding of Yahweh would have been destroyed. That is what had happened to the Zarahemlaites before the Nephites arrived. Alma is most interested in this real danger because the Ammonihahites pose just that threat to the greater land of Zarahemla.